1. Field of the Invention
This invention relates to a digital switching system, and more particularly to a digital switching system comprising line terminals which send and receive data as serial data to and from the user, a space-switching arrangement which switches, based on destination information, the parallel data converted from said serial data, and data converters which convert between said serial data and said parallel data.
2. Description of the Prior Art
A conventional digital switching system of this type is described in Japanese Patent Laid-Open No. 1-233858.This switching system comprises a serial/parallel converter circuit (1) which converts a plurality of fixed-length serial packet signals representing as a whole all the channels (n) to be converted, into a plurality (k) of parallel packet signals, a space-switching arrangement which comprises k matrices of (n/k)xc3x97(n/k) switches arranged in parallel and which converts k sets of parallel packet signals received from the serial/parallel converter circuit, and a parallel/serial converter circuit (3) which converts k sets of parallel packet signals received from the space-switching arrangement.
The conventional digital switching system described above, however, had a problem in that in order to change the capacity of the space-switching arrangement, it was necessary to change the capacity of the space-switching circuit itself or change the numbers of lines and space-switches.
Accordingly, the object of this invention is to provide a digital switching system capable of changing switching capacity without any recourse of increasing or decreasing the quantities of line terminals or cross-point switches.
The digital switching system according to a first aspect of this invention comprises line terminals which send and receive data as serial data to and from the user, a switching arrangement which switches, based on destination information, the parallel data converted from said serial data, and data converters capable of converting between said serial data and said parallel data at a specified conversion ratio.
The digital switching system according to a second aspect of this invention comprises N sending line terminals each of which receives serial data from the user, a serial/parallel converter having N serial/parallel converter circuits each of which converts the serial data into K-bit wide parallel data at the conversion ratio provided externally by mode selection information, a switching arrangement having M (Mxe2x89xa7K) cross-point switches of which K (Mxe2x89xa7K) cross-point switches select one bit each, based on destination information, from their respective assigned bit locations in said N sets of K-bit wide parallel data, a parallel/serial converter having N parallel/serial converter circuits which convert the K-bit wide parallel data received one bit each from said K cross-point switches, into serial data, and N receiving line terminals each of which sends said converted serial data to the user.
Furthermore, in the digital switching system according to the preferred embodiment of the invention, each of said serial/parallel converter circuits comprises a transceiver which converts said serial data into k1-bit wide parallel data; k1 variable converters having km serial/parallel converters of which k2 serial/parallel converters, in conjunction with a data-through circuit, convert one bit of the transceiver output into parallel data with a width of 2 bits, 4 bits, . . . , or km bits according to the mode selection information provided externally; and selector circuits which select output of each of said variable converters according to said mode selection information and output K-bit wide parallel data.